The present invention relates to a device for measuring moisture content in a grain such as a grain of rice and more particularly to an improved spring assembly provided in the device for adjusting pressure between a pair of roll electrodes which crushes a grain and measures the moisture content therein.
Japanese Utility Model Laid Open No. 62-35254 discloses a device for measuring moisture content where a pair of roll electrodes is provided to crush a sample grain one by one, and to detect the electric resistance in the grain between the electrodes. The detected electric resistance is converted to a voltage signal representing the moisture content in the grain.
In the device, a shaft of each roll electrode is supported by two bearings. A spring assembly comprising a coil spring is provided in each bearing of the shaft of one of the electrodes. The coil spring urges the electrode toward the other electrode so as to automatically adjust the pressure between the electrodes despite the variation of the size of the grain. Accordingly, the moisture content can be accurately measured.
However, in order to obtain a necessary pressure between the pair of electrodes, a coil spring having a large spring constant must be employed. Therefore the spring assembly inevitably becomes large, resulting in increase of the size of the measuring device. Furthermore, a complicated operation of adjusting the balance between both spring assemblies must be performed, causing high cost.